import { Settings } from "./index.svelte";
import { PUB_VERTD_URL } from "$env/static/public";
import { log } from "$lib/util/logger";

const LOCATIONS = [
	{ url: "https://eu.vertd.vert.sh" },
	{ url: "https://usa.vertd.vert.sh" },
];

export type VertdInner =
	| { type: "auto" }
	| { type: "eu" }
	| { type: "us" }
	| { type: "custom" };

export class VertdInstance {
	public static instance = new VertdInstance();

	private inner = $state<VertdInner>({
		type: "auto",
	});

	public save() {
		localStorage.setItem("vertdInstance", JSON.stringify(this.inner));
	}

	public load() {
		const ls = localStorage.getItem("vertdInstance");

		// if custom vertd url and no saved setting, default to the custom url
		if (!ls) {
			const isCustomUrl =
				PUB_VERTD_URL && PUB_VERTD_URL !== "https://vertd.vert.sh";
			if (isCustomUrl) {
				this.inner = { type: "custom" };
				return;
			}
		}

		if (!ls) return;
		const inner: VertdInner = JSON.parse(ls);
		this.inner = {
			...this.inner,
			...inner,
		};
	}

	public innerData() {
		return this.inner;
	}

	public set(inner: VertdInner) {
		this.inner = inner;
		this.save();
	}

	public async url() {
		const latency = async (url: string) => {
			try {
				const start = performance.now();
				await fetch(url, {
					method: "GET",
					cache: "no-store",
					mode: "no-cors",
				});
				return performance.now() - start;
			} catch {
				return Number.POSITIVE_INFINITY;
			}
		};

		switch (this.inner.type) {
			case "auto": {
				const results = await Promise.all(
					LOCATIONS.map(async ({ url }) => ({
						url,
						latency: await latency(url),
					})),
				);

				const fastest = results
					.filter((result) => Number.isFinite(result.latency))
					.sort((a, b) => a.latency - b.latency)[0];

				const latencySummary = results
					.map(
						(result) =>
							`${result.url} = ${Number.isFinite(result.latency) ? `${result.latency.toFixed(2)}ms` : "unreachable"}`,
					)
					.join("\n");
				log(
					["settings", "vertd"],
					`vertd latency results: ${latencySummary}`,
				);

				if (fastest) return fastest.url;

				// if none are reachable, fall back to custom
				return Settings.instance.settings.vertdURL;
			}

			case "eu": {
				return "https://eu.vertd.vert.sh";
			}

			case "us": {
				return "https://usa.vertd.vert.sh";
			}

			case "custom": {
				return Settings.instance.settings.vertdURL;
			}
		}
	}
}